Path: ...!3.eu.feeder.erje.net!feeder.erje.net!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!raubtier-asyl.eternal-september.org!.POSTED!not-for-mail
From: Bonita Montero <Bonita.Montero@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Namespace vs. class ambiguity: three compilers - three different
 outcomes
Date: Sat, 7 Sep 2024 20:42:26 +0200
Organization: A noiseless patient Spider
Lines: 52
Message-ID: <vbi6qd$1fpiu$1@raubtier-asyl.eternal-september.org>
References: <vbi5p0$1f8u2$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Sat, 07 Sep 2024 20:42:21 +0200 (CEST)
Injection-Info: raubtier-asyl.eternal-september.org; posting-host="8d495bec4d845596c9456083b69cf5b8";
	logging-data="1566302"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/dj8iwkPSL9cr4jnhLoy/qogBwR9z8nsg="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:3pxQeS7mhB2D3KzBf1BLAMu/3mY=
In-Reply-To: <vbi5p0$1f8u2$1@dont-email.me>
Content-Language: de-DE
Bytes: 2698

Am 07.09.2024 um 20:24 schrieb Andrey Tarasevich:
> Hello
> 
> It is illegal to just flat-out declare a class and a namespace with 
> identical names in the same scope
> 
>    namespace N {}
>    class N {}; // <- Not allowed
> 
> However, one can try to circumvent the direct restriction by means of 
> using-directive or using-declaration
> 
>    #include <iostream>
> 
>    namespace N
>    {
>      void foo() { std::cout << "namespace" << std::endl; }
>    }
> 
>    namespace X
>    {
>      struct N
>      {
>        static void foo() { std::cout << "class" << std::endl; }
>      };
>    }
> 
>    using X::N;
>    // or
>    // using namespace X;
> 
>    int main()
>    {
>      N::foo();
>    }
> 
> GCC is perfectly happy with either version of this code (both using- 
> declaration and using-directive versions are OK). It simply resolves the 
> call to the "namespace" version of `foo()`.
> 
> Clang issues an error: it complains about the call being ambiguous. I.e. 
> the error is issued at the point of the call.
> 
> MSVC++ issues an error for `using X::N;` at the point of using- 
> declaration: it basically says that `N` already exists in this scope. 
> But if we switch to `using namespace X;` version, MSVC++ will exhibit 
> Clang-like behavior: complain about ambiguity at the point of the call.
> 
> So, who is right here?

Does it really matter or is it just sufficient to prevent such code ?